Despite all the people who say you will die a horrible burning death and you computer will cause it if you dont upgrade, you will be fine. Not sure if the virus mobs will keep updating for XP, but if they do just make sure you stay up to date. You should make a conceded effort to upgrade why the time/money permits, as it makes it safer for you and prevents your computer being used as a method of attacking other servers.
Windows 8 is more or less the same as Windows 7. There is quite a few changes under the hood that the public does not see that makes it better, but for the average user it will make no difference. From your perspective, the big difference as you suggest is the user interface. For the layman, I would say get used to the new win 8 format, its better suited to those who are not technical. However if you are most comfortable with XP, then make sure you buy a computer with Windows 8.1 and get the shop to configure it so its like Windows XP.